He had flat feet, had slightly unusual leg bones (not bow legged, but a little bit of curve to them) overpronated and had a disproportionately long stride. And those defects to zero running experience, which means zero strengthening of connective tissue, and you had a recipe of IT band syndrome, which he suffered from every year (along with an occasional bout of bursitis, and some other nagging injuries).
His easy distance pace was probably around 6:40 freshman through junior years (15:10s to 14:50s), and dropped down closer to 6:00 his senior year when he broke through and ran those faster times, and that is fairly well in line with what you would expect of someone running those times.
Yes, if he would have been able to run 70 mpw and stay healthy he probably would have run faster. But to expect a new runner with some physical traits that lend themselves to an increased likelihood of injury to be able to run 70 mpw and stay healthy just wouldn't have been realistic for this runner.